For a Case, of Course
by WhatAThrowPillow
Summary: Johnlock - Sherlock needs to use John as a test subject for an experiment. There be lemons ahead.


**A/N: This is my first johnlock fic. Pure smut/fluff with some plot. You have been warned!  
**

**I don't own the characters. They belong to BBC? Sir Arthur Conan Doyle? ...anyway, they aren't mine.**

**Rated M! You have been warned twice!**

…

"I need you to take your clothes off now, John."

Sherlock paced the living room, palms together in deep thought.

"Sorry, what?" John's head spun with the possibilities and impossibilities. Sherlock simply couldn't be suggesting what he thought.

"I don't remember stuttering," he retorted.

He was doing that thing again, and John was defenseless against it. He wondered if Sherlock knew this – but of course he did.

"I don't understand," he managed to choke out.

Sherlock stopped pacing in front of the window and slowly turned around, his eyes lit up in unabashed excitement. "Don't you see? The woman in this case wasn't tortured with chains or whips or anything of the sort. That's why there aren't any marks on her body."

John waited patiently for the rest, his blood beginning to pump wildly in his veins.

When Sherlock didn't continue, John gave up and asked, "So how did they torture her?"

"Not _they_, John. _Him_. Keep up."

"Right."

"He was a former lover of hers, so he knew exactly what would make her _tick_." He emphasized the last word as he made his way slowly across the room. John was vaguely aware of the growing problem in his pants. Was he actually aroused? It seemed that the charm of Sherlock Holmes knew no boundaries. John was in too deep.

"How do you mean?"

Sherlock stopped inches away from John's face. The corners of his mouth twitched. "She was tortured in a different manner entirely. _Sexually_."

John gulped audibly. Was his face as red as he imagined it was? Was Sherlock aware of the effects he was having on his flatmate? _But of course_, John reminded himself again. He _was _Sherlock Holmes, after all. The man who could read a person by the kind of shoes they wore. And here he was, hovering over John like a predator ready to attack.

"H-how so?" John stuttered.

Sherlock stepped back, his face focusing back into concentration mode. John huffed in disappointment before he could stop himself.

"That's the thing. I won't know if my theory is correct until I test it out, of course." That glimmer in his eyes was back. "And, I believe you would be a fantastic subject to test on."

At this, John could no longer hide his arousal. Gay or straight, he could care less what he was now. He was simply smitten by Sherlock. Maybe this kind of sexuality belonged in a category of its own.

"Are you willing to give your consent?"

"I…uh, I…" John's words came out unexpectedly. _YES, he means YES_, his brain shouted. Sherlock's face fell only momentarily before he recovered.

"I suppose I could find another…"

"NO! Ahem, I mean yeah, sure."

"Yeah, sure? Have you any idea what you are getting yourself into?"

"Not at all." John tried in vain to keep his face passive, as if this would be just another one of Sherlock's crazy experiments. He wondered why Sherlock was grinning stupidly. Was it because he wanted to see John suffer, or because he was really interested in him? _Dammit,_ John repeated in his head over and over again.

"So what do you want me to do?"

Sherlock's hands came back together in front of his face. "Isn't it obvious?"

"Yes, well I supp…"

Without warning, Sherlock stepped closer, removing all the empty space between them. He looked down at John with intense eyes before slowly leaning in to kiss him.

John's body froze up the second he felt those soft lips on his. He was completely aware that this was, in fact, a man kissing him – no, it was Sherlock bloody Holmes, which was even wilder. How many times had John imagined this moment, only to shut it out of his mind in embarrassment? _This is really happening_, he thought.

Sherlock felt John tense up immediately. He didn't pull back, however, because it was transparently obvious that John wanted this. His military stance might have said one thing, but other parts of his body were saying exactly the opposite. Besides, he would back off any time if John said so. Sherlock slid his hand up behind John's neck. _Pulse is staggeringly high. Face is red and warm to the touch._

And then, John began to kiss him back. He was hesitant at first, but soon he just let go and embraced this strange turn of events. His tongue swirled in Sherlock's mouth before finding its way down his neck, determined to taste every inch of Sherlock.

Sherlock moaned before he could stop himself. _It's for a case,_ his mind tried telling him. He ignored it and watched as John fumbled with the buttons on his shirt.

"John…"

He began to tear off Sherlock's clothes in a blur. As he was undoing his belt, Sherlock placed a hand on John's shoulder to balance himself. It did nothing to stop John, who was already sliding Sherlock's pants down.

"John," he repeated breathily.

John looked up at him with blurred eyes. "Huh? What? Sorry."

Sherlock let out a small laugh. "It's me who is supposed to be doing the torturing, John."

"Right," he replied, throwing his hands up in mock defeat. Sherlock smirked again and leaned forward to kiss him on the forehead.

"Bedroom would be better suited for this sort of research," he said, trying to hide the shakiness in his voice. As determined as Sherlock was to let his boundaries down, his body was betraying him at this moment. After all, how many times had he lied awake at night thinking about this? _This is not for research, obviously. This is an innate desire stemming from your every being. Now focus._

John followed Sherlock into the room obediently, wondering just what the hell he had gotten himself into. It was clear that Sherlock was nervous, so John was certain that the whole experiment thing was simply an excuse to get him into Sherlock's bedroom. _Well, it has worked so far,_ he thought with a smile.

"On the bed," Sherlock said quickly.

John did as he said, but noticed the abnormally high pitch in the man's voice. "Sherlock, are you alright? You don't have to do this, you know."

"What? Yes, I'm fine." He ran his fingers through his curls.

"You sure? I mean, have you ever…er, done anything like this before?"

"No, why? Is it obvious?"

John couldn't help but smile fondly at his companion. He was so innocent in some ways, which were hidden to the rest of the world. He was showing his weaknesses only in front of John, which made him feel even more giddy.

"Not at all."

Sherlock got his nerves back under control – silly things, nerves – and leaned in to kiss John again. They kissed slowly at first, the heat pooling within Sherlock a new and welcome feeling. John pulled them both backwards on the bed until Sherlock was nearly on top of him. Sherlock ran his tongue over John's bottom lips if hesitantly asking for permission.

John let him explore his mouth at his own pace. Sherlock lost himself in the sensations that were overwhelming his body. He ran his hands down John's chest, loosening buttons as he went. John bit down on his lip to keep from gasping.

"No, none of that," Sherlock said breathlessly. "I want to hear you. It's…part of the…thing," he said in between kissing John's upper body.

"Thing?" John said distractedly.

"Experiment."

"Right."

Sherlock's kisses became more frantic and less innocent. He bit the side of John's neck and dug his nails into his hips. _Losing control,_ he reminded himself, forcing himself to sit up and breathe. John thrust his hips up in protest.

"Sher…"

Sherlock laughed almost wickedly. He hooked his fingers in John's belt loops and pulled his pants off. _Time for the show to begin._

John moaned loudly when Sherlock unexpectedly ran a tongue up his length. From there, his hands traveled to John's thighs, where they worked around his erect member menacingly.

"Sherlock, please," he heard himself say aloud. He looked down to see Sherlock in concentration mode. John would have sworn that this all really was for a case if he had not seen those dilated pupils and red face.

Sherlock licked John's cock again only once before beginning the assault on the rest of his body once more. John wasn't sure how much of this he could take before he cried out in agony. Please touch me, please…

"I am, John. Just be patient," Sherlock responded to the words John had not meant to say aloud. Now his tongue was swirling the tip, and oh God, it was heavenly. But then _fuck_, Sherlock's hands made their way up his chest and fingers circled his nipples.

"Ohhhh, please! Please Sherlock!"

Sherlock grinned again and took in a sharp intake of lustful breath before licking John's thighs and stopping just short of his cock once more. Finally, _finally_ he took John completely in his mouth. John could have sworn he came right then in there if the pressure had not continued to build. Whatever this magic was, he didn't want it to stop. No woman had ever made him feel this way before.

Sherlock moved slowly – much too slowly – before John was begging aloud again without realizing it. His small sounds and moans spurred Sherlock on, and before he knew it, Sherlock's concentration was clouded by his own desperate need for release. He paused for a moment, remembering that he was doing this for an…oh, to hell with it, he was doing this because he had craved John for months. John whimpered and Sherlock smiled, knowing that he was the one who was causing this primal reaction in John.

John thrust into Sherlock's mouth desperately and this caused an even bigger response in Sherlock, who sucked so fast and hard that John finally came with Sherlock's name on his lips. It was incredible, like nothing he had experienced before. His whole body went slack and he giggled as the feeling spread throughout his body.

He lifted his head to see Sherlock, still positioned between his legs, panting and smiling broadly. _Oh, love, how could I possibly leave you like that?_ John thought.

He sat up and kissed Sherlock soundly on the lips. "For an experiment, my ass."

"Yes, that's coming next," Sherlock responded. John laughed and pushed him back on the mattress.

"Oh. _Oh_," Sherlock said, the nervousness evident in his face.

"Relax, love. It's only me."

Sherlock's fears evaporated as John's light fingers traveled over his body. He planted sweet, small kisses everywhere until Sherlock was completely stripped down. His hands ran over Sherlock's hips – those hip bones were something John had not appreciated until now.

John began to stroke Sherlock as he kissed the side of his neck. "You've wanted this for so long, haven't you, Sherlock? You can say this was an experiment all you want, because I know the truth. You've wanted to fuck me since the day we met, haven't you?"

Sherlock responded with a small moan and closed eyes. There was something about seeing the great Sherlock Holmes rendered speechless that drove John crazy all over again.

"I bet you've fantasized about sucking my cock before, haven't you? That was all planned. Strategic."

Sherlock nodded as he thrust his hips up into John's hand.

"Well, so have I."

He moved down to where Sherlock was before and circled Sherlock's cock with his tongue.

"Yessss," Sherlock moaned in encouragement.

It was only a matter of seconds before Sherlock thrust up repeatedly into John's mouth, to the point where John had to hold those perfectly sculpted hip bones down. He came with a sharp intake of breath and looked down at John, who swallowed and licked his lips.

He slid back up the bed next to Sherlock, who was the most content that John had ever seen him.

"So?"

Sherlock reached out and grabbed John's hand. "The short version: amazing."

John noticed the hitch in his words. "And?"

"And…not for an experiment."

John searched those deep blue-green eyes for answers that he would likely never get.

Sherlock leaned in to him and they both drifted off into sleep. A while later, when the room was lit by the night sky, Sherlock awoke and stared at the perfect form beside him.

"John."

The man didn't so much as stir beside him, so Sherlock whispered the words he had been dying to say earlier, but couldn't find the right moment.

"I love you, John. I am so in love with you. I know love is a dangerous disadvantage, but I am prepared to make the exception for you."

There was a slight twitch in John's lips, but he continued breathing soundly. Sherlock smiled and closed his eyes once more.

_I love you too, you ridiculous man_, John thought happily.

…


End file.
